Karyopherin

Karyopherins are a group of proteins involved in transporting molecules from the cytoplasm into the nucleus of eukaryotic cells. The inside of the nucleus is called the karyoplasm (or nucleoplasm). Generally, karyopherin-mediated transport occurs through the nuclear pore, which acts as a gateway into and out of the nucleus. Most proteins cannot traverse through the nuclear pore by themselves, but require karyopherins.

Karyopherins, can act as importins (i.e. help proteins get into the nucleus) or exportins (i.e. help proteins get out of the nucleus). They belong to 9.A.14 The Nuclear Pore Complex Family in the transporter classification database (TCDB).

Energy for transport is derived from the ran gradient. See Ran for further details.

Contents

Importin beta example

Importin beta, a karyopherin, facilitates transport of cargo proteins into the nucleus. It does this by first binding importin alpha (another karyopherin) which binds the cargo protein in the cytoplasm. The cargo protein is imported into the nucleus through the nuclear pore, using energy derived from the Ran gradient. Once inside the nucleus, the cargo dissociates from the karyopherins. It has therefore been transported from the cytoplasm to the nucleus.

Importin beta can also carry proteins into the nucleus without the aid of the importin alpha adapter protein.[1]

Human genes in the karyopherin family

Additional images

References

  1. ^ Poon, I. K. H. and D. A. Jans (2005). "Regulation of nuclear transport: Central role in development and transformation?" Traffic 6(3): 173-186.

External links